Re: [tip:locking/core] locking/atomics: Check generated headers are up-to-date

[Ingo Molnar <mingo@kernel.org>]

* Mark Rutland <mark.rutland@arm.com> wrote:

> > Could we please get this fixed so that proper dependencies are checked 
> > and it's only regenerated when needed? This slowdown makes additive-build 
> > kernel development quite painful, as ~5 seconds is in the 'too long' 
> > category already, while 1.2 seconds is basically instantaneous.
> 
> Just to check, are we happy to eat the full cost for the first build of a
> pristine tree?

No, not happy to add 3-4 seconds to a full build that usually takes less 
than 60 seconds. This stuff isn't parallelized nor particularly well 
optimized it appears.

This *must* get faster.

> One reason we do the check rather than (re-)generating the headers is 
> that Linus requested [1] the generated header be committed so that they 
> show up in git grep, but it looks like he was happy to be flexible on 
> that.

I think the generated headers should be part of the commit space, the 
grepping is important.

> If we're happy to not commit in the generated headers, and if we're happy to
> pay the cost for a pristine tree, that's fairly straightforward to do.
> Otherwise, this has to be an optional check.

Or faster code, or a different concept!

Thanks,

	Ingo